I'm taking a class in language acquisition called "Nature vs Nurture". I'm not particularly fond of that framing, because the divide seems overly dichotomous. In addition, the N-vs-N debate has been used as a tool of oppression throughout history, namely in eugenics. So I'm wondering, Are there any cases in linguistics of this debate being used for harm?
The so-called "nature vs nurture" debate in linguistics is not as dichotomous as it may seem from the first sight.
Everybody agrees that humans have innate abilities that enable them to learn language. (By "everybody" I mean Chomsky, Pinker, Jackendoff, Goldberg, Langacker, Lakoff, Evans, and basically any linguist from any possible camp.) It is obvious to everyone, as that's the only sensible explanation of why people learn language while other animals don't.
Everybody agrees that the development/acquisition of language requires right environment. There have been cases of people who weren't exposed to any language in their childhood and didn't learn any language. Again, that's something completely uncontroversial.
The only real point of controversy (a relatively minor controversy, if you ask me) is whether the structures in our brains that enable us to learn language are language-specific or not. The generative grammar camp postulates that some of our language acquisition abilities are specific to language and not used for anything else. The cognitive linguistics camp tries to account for language learning based on our general, non-language-specific learning abilities.
I can't see how the controversy about language-specificity of our language learning abilities can be a source of any harm or oppression.
Nurture vs nature have crisscrossed with discrimination basically by radicalising discrimination into attempts of extermination when the discriminating party believed that the traits they discriminated against were genetic, ie, based on nature, not nurture.
There certainly has been discrimination against languages along history, and there certainly were historical attempts to eradicate languages. But I don't think that there was any attempt to exterminate the speakers of a language, purely based on the fact that they spoke that language, and, that language being "inferior" or noxious, plus the speakers being somehow genetically bound to that language, they should or could be exterminated.
On the contrary, the deliberate attempts to eradicate languages seem to have all been based on the notion that languages are learned - and were undertaken exactly by the method of teaching the preferred language to the discriminated language speakers, or to their children.
In Europe, the attempts to eradicate languages - Breton in France, Galician, Basque and Catalan in Spain, several dialects in Italy, perhaps Welsh in the UK - seemed much more based upon the idea of imposing linguistic uniformity upon the territory controlled by a State, not so much upon the idea that the targeted language was "inferior". When Europeans did that abroad, the notion that native languages were "inferior" was much more publicised (just look at how those languages are pictured in Western comics, for instance the quite notorious The Phantom), but even there the main effort seems to have been to teach the natives a European language, not to deliberately kill them for the sake of it (nevermind brutal exploitation - and political repression intended to support such exploitation - having quite genocidal effects during the colonial era).
Nowadays, however, the "nature vs nurture in languages" debate seems to focus not on whether we are hardwired to a given language, but whether we are hardwired for language in general. It seems well established that all people can learn any language, and that their first language will be determined by the language spoken around them during their early childhood, not by any innate factor. It seems also well established, at least in an academic level, that languages are similarly complex in syntax, no thing such as a "primitive" language actually existing, and, regarding morphology, the correlation is inverse, ie, languages of more simple societies have a more, not less, complex morphology.
Within that frame, it would be difficult to effectively use the "nature" side of this debate to oppress or discriminate people. Linguistic prejudice, which is far from rare, usually takes for granted that "bad" language is the result of a defective education - and it is that defective education that is discriminated against.
(But then there is this quite extraordinary thing with the Pirahã language, which supposedly has no embedded clauses, and makes its first-language speakers unable to grasp the concept of numbers. If the Pirahã were millions of people, and effectively engaged in the process of production of commodities, instead of a few thousand hunter-gatherers - or, on the contrary, if they were somehow harming the prospects of economic exploitation of the region they live in - I would fear those notions could be used as a tool against them.)